I'd imagine the bogie tender was for range, not so much for some aggressive hunger. I don't know the operating climate in Nigeria with any detail, though. Probably had longer uninterrupted runs with no chances to replenish fuel or water than is practice in the UK. UK service could probably afford a three-axle tall tender.
In re my suggestion of a 4-8-0 King, @The Johnster, my suggestion was more to increase the King's viability for regular service. Even taking the King down to Red availability increases her access twofold. As @JimC mentions, just the basic math for another axle dividing the same weight down brings the King under by 125lbs/axle. Admittedly, additional frame and another set of 6'6" drivers weighs more than 1500lbs. So, also by his suggestion, reducing the wheelsize to something like 5'8" could maintain the desired performance, while keeping the total weight within the axleweight limit.